Uric acid which is a pathogenic substance of gout is synthesized by xanthine oxidase in the human body. Accordingly, inhibition of xanthine oxidase is useful for treatment and prevention of gout. In fact, allopurinol which is known as a therapeutic drug for gout is a useful xanthine oxidase inhibitor.
The present inventors have studied xanthine oxidase inhibitors contained in edible plants, and found that a component having xanthine oxidase inhibitory activity is present in edible plants of Labiatae, Compositae and Liliaceae, and an extract of these plants is useful for treating hyperuricemia. The present inventors have filed a patent application directed to a pharmaceutical composition for improving hyperuricemia comprising as an active component an extract from these plants (Japanese patent application no. 1-213998).
The present inventors have further studied the above active component and have succeeded in isolation and purification of active compounds from plants of Labiatae.